Speed wobble issues. Any advice...?

bristolpete

Hi,

I am lucky enough to own a Cervelo S3

I am very happy with the bike, but today that feels more like 'a was' as it is exhibiting shocking amounts of speed wobble when descending. Out on a 60 mile ride last weekend it began and was a little bit of a shock, but manageable. However, today it was unbelievable and to be honest terrifying as the whole bike shook. It were as if bit by bit it was going to come apart. It was so bad that it threw my water bottle from the cages (nightmare as 35 miles away from home on a warm day). A car driver ran over my bottles and once I managed to slow the bike and pull over she stopped. She asked if I was OK. I said, I was pretty shaken (excuse the pun). Naturally she said she had never seen that before, to which I advised nor had I. Being honest, I was literally shitting myself.

It kicks in between 30 mph - 40mph +. Oddly today, according to my ride data my top speed was 40 pmh which is actually 2 mph slower than last weeks events when the wobble took also effect. Paradoxically, it was far worse on a slower hill.

Desperate to work this out as I had/have considered the S3 my dream bike for two years and dont want to have wasted £3.5k of my hard earned savings on a frame that I can either hold back or frankly not ride at all. Based on todays experience I would prefer not to ride it what so ever as crashing would be inevitable.

Any advice gratefully received. As a heads up, I am 14 stone, 5 foot 8.5", solid experienced rider, built for the flat as they say. Previous rides of late include Kuota, Pinarello of which nothing did this. In fact I have never had a bike do this period, including DH MTB.....

At the moment, I am gutted, but want to work out whats causing it.

JamesB

From what I understand and saw with another riders bike last year, which also produced a terrifying jelly like speed wobble, there are a vast number of factors that may cause it, and it may even be insoluble (sorry:(!)
Wheels may have an effect, if bike has been OK up to now how about frame failure??
On a happier note I heard of changes to seatpost (amazingly) and handlebar stem (more understandable) can cause / stop speed wobble. Worth doing a web search on subject too. (Chris Juden CTC I think has big article on this subject)
Go back to the point of sale also
best wishes

balthazar

There isn't a single cause or an easy fix. Read this article...

http://www.sheldonbrown.com/brandt/shimmy.html

...for a clear explanation of the phenomenon, and some advice. Good luck.

frazerbrown

I am no expert, but have suffered from speed wobbles in the past. After a massive crash it was suggested it was down to the tyres. Not sure if it was or not personally, but it might be worth checking them out if they've been on the bike a while.

bristolpete

Thanks guys. Bad news indeed.

SteppenHerring

It's a resonance thing so small tweaks might affect the speed at which it happens - or stop it altogether. On the other hand, I see that tweaking, then scaring the cr@p out of yourself repeatedly might not be a fun way to spend time - although the hill repeats would be good training.

bristolpete

Yeah - I don't know if I should laugh or cry to be honest. I think the bike will be deconstructed bit by bit and then taken out, but if it continues, I have no desire to ride it. Quite how I kept it upright today is a mystery to me seeing as it threw bottles out cages that have sustained time on Flanders pave....

fixie71

Speed wobble! happened to me twice, different bikes but both times there was a commom factor. The first time I was 0n the A6 doing a time trial, obviously speed was not a factor as I am decidedly slow, a very large waggon went by and the draught started the wobble that I managed to come out of after being scared witless. The second was screaming down Blackstone Edge when I got caught by a side wind on a wide bend. This also started a wobble, at speed this time, I was so worried I was looking for a grass verge to hop on to but in this area stone walls prevail. Scared the life out of me this one. On niether bike did it ever occur again so I put it down to the sudden draughts taking my front wheel.

Anonymous

I used to have speed wobbles on my Siena. I no longer have them, here is what I do to prevent it.

When descending, place the pedals horizontal so both knees are bent and place one knee on the top tube. Slightly unseat yourself a few mil off the seat. Try not to tense up and have a relaxed grip on the bars. I also found I had more wobbles when getting cold, ie on a chilly ride descending before getting warmed up, shivering seemed to help induce the wobble.
Relaxing is very important, always have a line of descent in your head, scrub off speed before a corner if you are doubtful. the one thing I used to do but dont need to now, is put my tongue between my teeth. If you tense up, you will bite down on your tongue, it just reminds yourself to calm down and take control.
I felt exactly the same way, spent £3k on a litespeed and dreaded riding it for a while. Also practice descending, get comfortable with it and you and your Cervelo will be fine.

JamesB

dmclite wrote:

I used to have speed wobbles on my Siena. I no longer have them, here is what I do to prevent it.

When descending, place the pedals horizontal so both knees are bent and place one knee on the top tube. Slightly unseat yourself a few mil off the seat. Try not to tense up and have a relaxed grip on the bars. I also found I had more wobbles when getting cold, ie on a chilly ride descending before getting warmed up, shivering seemed to help induce the wobble.
Relaxing is very important, always have a line of descent in your head, scrub off speed before a corner if you are doubtful. the one thing I used to do but dont need to now, is put my tongue between my teeth. If you tense up, you will bite down on your tongue, it just reminds yourself to calm down and take control.
I felt exactly the same way, spent £3k on a litespeed and dreaded riding it for a while. Also practice descending, get comfortable with it and you and your Cervelo will be fine.

Surely all of this should not be at all necessary on any bike???
I tried to get a speed wobble last year following seeing another riders problems, by shaking bars , taking hands off---not matter waht I did any initial wobble subsided almost immediatley No bike should develop speed wobble!

dag_on_a_bike

Been there and hit the deck at 38mph!

See http://www.bikeradar.com/road/fitness/article/qa-speed-wobble-14776

and

http://www.bikeradar.com/road/forums/viewtopic.php?t=12585336

also

http://www.bikeradar.com/road/forums/viewtopic.php?t=12591241

Body's 'fixed' and bike's fixed (arguably better) but to this day, 18 months later, I still don't have the same confidence when descending.

bristolpete

Cheers. Having had 24 hours to digest it, I cant stress, nor can words on a forum advise on how utterly bad it was. I could 'man up' as people say, but after having a bad crash last year I dont want to go down what so ever. As I said, quite how I kept the thing upright is a mystery to me.

I have googled loads and it seems this issue could be numerous things, but a permutation of things that lead to it happening. The real issue is that if I cant get rid of it, I don't want the bike, and that is simply mad.

Part of the fun of climbing a long hill is the descent on the other side. Holding back at 20mph on the brake is no fun at all.

Overall, very deflated at the moment.

dixiesurf

Hi
I had the same problem on my Cervelo RS when descending in the Dolomites at 40+ mph and it is truly scary it felt as if the the rear triangle was coming away from the main frame!!! What worked for me was swapping my wheels with a friend and doing it all over again, this time no speed wobble. I then changed the tyres and tubes and never experienced it again I now have a 2010 S2 and so far the bike has been a dream
As somebody mentioned earlier there are many factors that could influence the problem but I reckon tyres and tubes is a good staring point..

desweller

I think dmclite has good advice. The key I think is to limit your feedback with passive damping, which is what pressing your leg onto the top tube does.

If you have a wheel imbalance you might be able to feel it by taking the wheel off the bike and giving it a spin while holding onto the axle.

JamesBwmb, I doubt any bike builder has ever done a frequency response analysis on a bike, besides which the spring/damper response of the human body is poorly understood anyway. Given all that it's not that surprising that some bike/rider/wheel combinations will suffer from resonant vibration from time to time.

rake

i wonder if it could be the wheels being out of balance, which could be affected by the tyres and tubes varying thickness and also the rim joint. if you turn the wheels fast while the bike is upside down the bike shakes quite violently. at the right speed this could cause the bike to resonate into a speed wobble. just a thought. solving it with different tyres could be in support of this idea. like car wheels unbalanced causes the steering wheel to resonate at a certain speed.

nipon

Could you not get someone else to have a go on your bike,at least then you will know if somethings not right with the bike or the way you ride.

frazerbrown

nipon wrote:

Could you not get someone else to have a go on your bike,at least then you will know if somethings not right with the bike or the way you ride.

I think you'd need brave/ kamikaze friends!

mercsport

I've had a long history of speed wobbles and never worked it out as to the 'why' of them. However strangely, perhaps, is the fact that the lightest bike I've ever had never displays any hint of shimmy. And the one before -come to think of it - both of them titanium ( might be a factor - one of many).

A short illustrative vid' here, although the real problem is when your hands are on the bars normally and the cycle enters into its capers :

http://www.youtube.com/watch?v=xODNzyUbIHo

Anonymous

JamesBwmb wrote:

dmclite wrote:

I used to have speed wobbles on my Siena. I no longer have them, here is what I do to prevent it.

When descending, place the pedals horizontal so both knees are bent and place one knee on the top tube. Slightly unseat yourself a few mil off the seat. Try not to tense up and have a relaxed grip on the bars. I also found I had more wobbles when getting cold, ie on a chilly ride descending before getting warmed up, shivering seemed to help induce the wobble.
Relaxing is very important, always have a line of descent in your head, scrub off speed before a corner if you are doubtful. the one thing I used to do but dont need to now, is put my tongue between my teeth. If you tense up, you will bite down on your tongue, it just reminds yourself to calm down and take control.
I felt exactly the same way, spent £3k on a litespeed and dreaded riding it for a while. Also practice descending, get comfortable with it and you and your Cervelo will be fine.

Surely all of this should not be at all necessary on any bike???
I tried to get a speed wobble last year following seeing another riders problems, by shaking bars , taking hands off---not matter waht I did any initial wobble subsided almost immediatley No bike should develop speed wobble!

It does happen, no rhyme or reason for it. just trying to help someone as I was helped. I now descend pretty well and was happy with using the techniques. just cout yourself lucky you haven't had a wobble even when trying to induce it.

JamesB

dmclite---yes very much so I do ; I`ve had speed wobbles on laden tourers and not good at all , but fortunately never any effects as you and others have had

Wappygixer

What wheels are fitted? I know lots of people say radial spoked wheels can be a nightmare on some bikes when decending.
Only way to test this is like its been said above is to try different wheels.

rake

how do you sit when descending. hover on the seat and stand on your feet, it seems far more likely if all of your weight is on the seat ie high up. it can happen on a motorbike too called a tank slapper as the bars hit either side of the petol tank.

Lynx_516

Given a specific bike speed wobble will occur if there is insufficient steering damping which results in an wobble which increases in size with time rather than decreases.

So to prevent a speed wobble you need to increase the damping of the steering (i.e. you) This can be done by relaxing a bit more, or in the case that this isn't enough, increasing how much weight you place on the handle bars should reduce the frequency of the wobble enough for it to be controlled.

It is odd that the understanding of this phenomenon is not known more as it is a well known issue in the steering of all vehicles and is usually designed out.

bristolpete

Thanks for the input all.

The issue is well in hand with my LBS shop which reminds us of why we support and choose to buy kit from them as you cant fault top notch service. I will take on board all advice and the shop are looking at set up and kit to iron out the said wobble.

I feel positive that it will be removed. Of course, knee jerk reaction is to hate the bike. I dont, I just want to rid it of the issue. On a positive, I hammered out 65 miles on the bike and said to a friend how great it is to ride.

I have concluded that it is much like 88 mph in Back to the Future. The variables kick in and away you go - so to speak...!

Chris James

bristolpete wrote:

Any advice gratefully received....

At the moment, I am gutted, but want to work out whats causing it.

I had it on an old 531c frame after I had swapped out tyres for narrower ones. I only ever got it near the beginning of rides, when heading down steep hills.

In the end I decided that the tyres had kicked it off, and subsequent reccurrences were down to me over tensing!

The knee on top tube trick works, but alos relaxing worked for me (difficult if you half expect tank slapper to start at any moment).

I had ridden the bike for 15 years fine before it shimmying the first time. I ended up blaming the tyres and myslef!

passout

Never had it myself but I read on BR somewhere about similar experiences. One guy (forget who) said something about a crack in a carbon steerer tube causing it, although the aforementioned mentioned wheel balance thing seems as likely as anything.

datpat64

Hi Mate

I've just experienced precisely same thing on a Specialized costing me best part of £2500. Did you manage to sort it out ? Had scary experience on the Cat and Fiddle where there's barely roon to bale out or even pull to the side and I'm currently riding my winter bike as I'm a bit worried about getting back on Specialized. let me know how you got on mate

Dave

PeeDee

Having ridden many thousands of miles without incidient on my Specialized Allez Comp, one day out of the blue I got a horrendous speed wobble descending a long fast descent in Colorado US. So bad I couldn't even see the road ahead because my head was being shaken about so much.

Same bike, same wheels, same rider, same tyres, same everything. Luckily it has been a one-off on that bike. I had a Dawes Galaxy that always wobbled when laden, but that had been crashed, so I think the frame was bent anyway.

If you still get a speed wobble regularly, even after practicing sitting light in the saddle, not gripping bars too tight etc, then I guess its time to think about swapping your bike for a different one. You might just be unlucky in being exactly the right weight and shape to form a perfect oscilator with your frame. Bummer.

bristolpete

datpat64 wrote:

Hi Mate

I've just experienced precisely same thing on a Specialized costing me best part of £2500. Did you manage to sort it out ? Had scary experience on the Cat and Fiddle where there's barely roon to bale out or even pull to the side and I'm currently riding my winter bike as I'm a bit worried about getting back on Specialized. let me know how you got on mate

Dave

Yes, it was nothing more than a loose nut in the headset, but as before, it was more about the permutation of everything happening on that hill at that time. I did not experience after that at all.